http://www.army.mil/modularforces/index.htmits very interesting it seems like there abandoning the concept of the "Division" as we know it. instead the primary unit will be the Brigade Combat Team, so basically any 3 or 4 brigades combined with a Divisional Headquarters will form a Div.
from what i gather in theory, say a Theater commander is granted command of a Div. he is then given command of 3-4 different brigades that could be each from a different division, they would then be assembled under a Divisional Headquarters and would act as one unit, the Brigades will however with 2 exceptions still retain there "Lineage", as in History, tradition, unit colors and so on.
it does seem like a very interesting concept that would allow them alot more fexibility because in as i understand it a commander can pick and choose units depending on the mission and have 1 Airborne, 1 Armored and 1 Infantry brigade act together as one Div.
edit from a tournament stand point its pretty cool because we can assemble dif brigades historically from dif divisions and assemble them under one divisional title